This invention relates to railroad crossties and particularly to novel crossties advantageously replacing wooden ties conventionally used to support rails on a railway roadbed composed of particulate ballast.
Although wood ties have been and continue to be generally used in railroad track construction and maintenance, other materials have been sought and suggested for use particularly where the inherent characteristics of wood make wood ties unsatisfactory or where the scarcity or cost of suitable timber for wood ties makes substitute materials attractive. To this end, ties fabricated of concrete or of metal have been suggested. However, such ties are extremely heavy or awkward to use compared to wood ties, and concrete is brittle and nonresilient.
It has also been suggested to fabricate ties from synthetic plastic resin compositions. For example, ties fashioned from 20-lb/cu. ft. density polyurethane foam encased in an outer envelope of glass-reinforced polyester resin were described in a publication in "Modern Plastics", August, 1967, page 96. Ties constructed of cellular theremoplastic polymer, such as polyethylene, having density between about 20 and about 50 pounds per cubic foot, are described and claimed in U.S. Pat. No. 3,813,040 (May 28, 1974) to Ben W. Heinemeyer. These ties were designed to look like wood ties, i.e as generally rectangular blocks having the length, width and height of standard wood ties cut from natural logs.
Another synthetic tie, described and claimed in U.S. Pat. No. 3,416,727 (Dec. 17, 1968) to Benjamin P. Collins, is molded from a composition of pinewood resin modified phenol formaldehyde resin and shredded hardwood filler.
An object of this invention is to provide a new and advantageous crosstie for use in conventional railroad track systems, particularly to support and secure rails on a railway roadbed composed of particulate ballast such as crushed rock.
Another object is to provide such crossties which are lighter in weight and more durable than wooden ties but which have at least comparable holding power to maintain the rails in position on the roadbed.
Other objects and advantages of the new crossties will become apparent in the following description.